Note 14 - Credit Risk and Concentrations

Financial instruments that subject the Company to credit risk consist principally of trade accounts receivable and cash and cash equivalents. The Company performs certain credit evaluation procedures and does not require collateral for financial instruments subject to credit risk. The Company believes that credit risk is limited because the Company routinely assesses the financial strength of its customers and, based upon factors surrounding the credit risk of its customers, establishes an allowance for uncollectible accounts and, consequently, believes that its accounts receivable credit risk exposure beyond such allowances is limited.

The Company maintains cash deposits with financial institutions, which, from time to time, may exceed federally insured limits. Cash is also maintained at foreign financial institutions for its Canadian subsidiary and its majority-owned Saudi Arabia subsidiary. Cash in foreign financial institutions as of June 30, 2018 and December 31, 2017 was immaterial. The Company has not experienced any losses and believes it is not exposed to any significant credit risk from cash.

The following table sets forth the percentages of revenue derived by the Company from those customers which accounted for at least 10% of revenues during the six months ended June 30, 2018 and 2017 (in thousands):

The following table sets forth the percentages of revenue derived by the Company from those customers which accounted for at least 10% of revenues during the three months ended June 30, 2018 and 2017 (in thousands):

As of June 30, 2018, Customer A represented approximately 22%, Customer B represented approximately 17%, and Customer C represented approximately 15% of total accounts receivable. As of June 30, 2017, there were no customer concentrations greater than 10% of total accounts receivable.

As of June 30, 2018, two vendors represented approximately 36% and 20% of total gross accounts payable. There were no purchases from these vendors during the three and six months ended June 30, 2018.  As of June 30, 2017, one vendor represented approximately 40% of total gross accounts payable. Purchases from this vendor during the three months ended June 30, 2017 were $4.1 million. Purchases from this vendor during the six months ended June 30, 2017 were $5.8 million.